Tush G M, Kuhn R J
Department of Pharmacy and Pharmaceutics, Medical College of Virginia/VCU, Richmond, USA.
Ann Pharmacother. 1996 Nov;30(11):1251-4. doi: 10.1177/106002809603001109.
To report a case of methemoglobinemia induced by benzocaine and resorcinol (Vagisil) cream, an over-the-counter medication that was used to treat diaper rash in a neonate.
A 6-day-old, 3350-g white boy was found to be cyanotic with blue mucous membranes on presentation. He had a diaper rash that was red and irritated, which his mother had treated with Vagisil cream. Methemoglobinemia secondary to absorption of benzocaine and resorcinol (1,3-benzenediol) from the Vagisil was diagnosed, with a methemoglobin level of 35% on admission (normal 0.4-1.5). Intravenous methylene blue 3 mg (1 mg/kg) was given; the neonate's skin color returned to normal 45 minutes after the dose.
Methemoglobinemia is a condition in which hemoglobin is oxidized to the ferric form. Oxidized hemoglobin, methemoglobin, is incapable of reversibly binding oxygen at the physiologic partial oxygen pressure. Main causes of methemoglobin formation are exposure to certain oxidizing agents and drugs, deficiency of one of the enzymes necessary for reduction of methemoglobin to hemoglobin, or the presence of an abnormal hemoglobin resistant to reduction. Clinical manifestations of methemoglobinemia include diffuse slate-gray cyanosis with low oxygen saturation in the absence of respiratory distress. A single intravenous dose of methylene blue 1-2 mg/kg is the treatment of choice.
Newborn infants are at increased risk for methemoglobinemia due to diminished enzyme systems required to reduce ferrihemoglobin to ferrohemoglobin, as well as because fetal hemoglobin is more easily oxidized than is adult hemoglobin. It is important to recognize possible drug reactions and educate parents on the potential risks of treatment with over-the-counter medications, especially in neonates.
报告一例由苯佐卡因和间苯二酚（Vagisil）乳膏引起的高铁血红蛋白血症病例，该非处方药物用于治疗一名新生儿的尿布疹。
一名6日龄、体重3350克的白人男婴就诊时被发现面色青紫，黏膜呈蓝色。他患有尿布疹，发红且有刺激症状，其母亲用Vagisil乳膏进行了治疗。诊断为因从Vagisil中吸收苯佐卡因和间苯二酚（1,3 -苯二酚）继发的高铁血红蛋白血症，入院时高铁血红蛋白水平为35%（正常为0.4 - 1.5）。给予静脉注射亚甲蓝3毫克（1毫克/千克）；给药后45分钟新生儿肤色恢复正常。
高铁血红蛋白血症是一种血红蛋白被氧化为三价铁形式的病症。被氧化的血红蛋白，即高铁血红蛋白，在生理氧分压下无法可逆地结合氧气。高铁血红蛋白形成的主要原因是接触某些氧化剂和药物、将高铁血红蛋白还原为血红蛋白所需的一种酶缺乏，或存在抗还原的异常血红蛋白。高铁血红蛋白血症的临床表现包括在无呼吸窘迫情况下出现弥漫性石板灰色青紫且氧饱和度低。单次静脉注射1 - 2毫克/千克亚甲蓝是首选治疗方法。
由于将高铁血红蛋白还原为亚铁血红蛋白所需的酶系统发育不全，以及胎儿血红蛋白比成人血红蛋白更容易被氧化，新生儿发生高铁血红蛋白血症的风险增加。认识到可能的药物反应并就非处方药物治疗的潜在风险对家长进行教育很重要，尤其是在新生儿中。
